This invention relates to a feeler unit for positioning sheet glass processing tools.
As is known, sheet glass is laid, for processing of the sheet edges thereof, onto a supporting table which is driven to bring the edge of the sheet below a working head which will effect the edge processing.
Since the edge of the glass sheet is below the working head of the processing tools it will be understood that this invention is concerned with sheet glass processing machines, the processing tools of which are arranged above the glass sheet.
In order to follow the profile pattern of the edge, feeler units or assemblies are used which sense the profile pattern of the edge and pilot the tool holder to direct and position it in a desired way.
Such feeler units include one or more edge-following rollers which engage with the sheet edge, or even with a template placed underneath the glass sheet, to follow the profile thereof.
Further, a back-up roller is usually employed which supports the glass sheet from underneath to oppose any flexing of the sheet under its own weight.
With prior feeler units, it is recognized that, as the feeler unit is positioned relatively to the sheet edge and especially where no template is used, the back-up roller tends to strike the glass sheet with some force, which may result in local damage to the sheet, thus producing a defect therein which, albeit of minor import, still is quite noticeable.
In an effort to remove that drawback, it has been common practice to provide in some cases for a slight bevelling of the edge bottom end to prevent any damage from impact as stated above, but this procedure, additionally to affecting the quality of the product, involves an additional processing step that reflects unfavourably on the overall cost of the finished product.